The present invention relates to a sensor and a seal for a sensing element of the sensor. U.S. Pat. No. 5,467,636 describes a known sensor in which a planar sensing element is immobilized in gas-tight fashion, by way of a sealing element, in a passthrough of a ceramic shaped element. The ceramic shaped element has, on the end surface facing away from the exhaust gas, a recess which surrounds the passthrough and into which a fusible glass seal is introduced. The fusible glass seal surrounds the sensing element in gas-tight fashion at this point, and creates a gas-tight connection to the ceramic shaped element. The fusible glass seal is the only sealing element which implements the seal between sensing element and ceramic shaped element.